Method of distilling oils



@Y lrJZn Q |V s XUOP Q G T... G H M 3. ozromj 3 m m Y G. G .G O M U m L@ G (S O D M Gf) NN C F M G G G O d B E :00.5% HU 'TN nu. wm wzromqj v K G G E M MN a a )N w Nw Y GW LSVIJ d la w G 9 nl 9 N QM. Y QN Patented Mar. 31, 1936 UNITED STATES PATENT OFFIQE METHGD 0F DISTILEING OILS Application- March 23, 1933, Seria-I No. 662,276

3 Claims.

The present invention relates to methods of distilling oils.

In general, the crude oils most amenable to fractionationv are those in which there is no great disproportion between the quantities of th'e several oil groups of the mixtures. These groups comprise the greater part of theV so-cal-led mixed base crudes, as wellas some of the asphalt base and paraiiin base crudes. There are, however, some crude oils of unbalanced composition, in which there is an excessive proportion of either the lighter or heavier ends. For example, Coalinga crude contains only about 5% of gasoline and about 20% of components ordinarily designated as gas oil, the remainder being made up of lubricating stock and asphalt. Fractionation of such crude is difcult because recovery of even the lightest ends may require heating of the entire crude to a temperature at which the heavier material will crack.

According to the present invention, fractionation of such unbalanced crudes is facilitated by reducing them to approximately standard specifications, preferably by the introduction of light materials to bring up the proportion thereof with respect to the heavy ends. Preferably, the amount of material added in any case will be such as to reduce the material to a composition having about one-third light material', one-third lubricating stock, and one-third asphalt. By light material is meant' a mixture of those components starting' from the lightest ends and including the fraction ordinarily designated as gas oil,-that is to say, a mixture of components having atmospheric boiling points up to about 650 F. In the case of a Coalinga crude, a satisfactory reduction Vcan be obtained by the addition of kerosene. Although the introduction` of kerosene alone does not produce an exactly balanced mixture of light, intermediate and heavy materials, it affords a mixture of suicient balance for satisfactory distillation.

The crude thus altered is heated, and then introduced into a column wherein the lighter materials are distilled off and fractionated. The

presence of the augmented body of light material permits vaporization at a suiiiciently low temperature to prevent cracking. The residuum from this primary distilling operation comprises a mixture of lubricating stock and asphalt which is then preferably treated in accordance with the disclosure of my U. S. Patent No. 1,905,156, namely, by the introduction of a diluentl which may be the kerosene previously recovered in the first column, followed by heating and ash vaporization under vacuum. As a result, the lubricating stock and the diluent are completely vaporized from the asphalt, the oils may be separately condensed, and the kerosene returned as diluent to the primary distillation in the first column.

(Cl. 19E-88) As another example of reduction to standard specifications, a heavy crude, such as Coalinga, may be initially mixed with an unbalanced light crude. A typical light crude of unbalanced proportions is a Kettleman Hills crude, which may have a gasoline content higher than 60%, with only a small amount of lubricating components, and little or no asphalt. Such a crude is also difficult to fractionate, but for a different reason, namely, that the vaporization of the lighter materials tendsl to carry over the heavy oils, which cannot beV suppressed from the vapors except by excessive refluxing, and then only incompletely. Accordingto a modification of the present invention, a heavy and a light crude, represented by Coalinga and Kettleman Hills crudes as typical examples, are mixed and subsequently distilled. In such a case, the mixture is such as to produce reasonably favorable proportions of the light, intermediate and residual materials.

The accompanying drawing is a diagram of the preferred form of apparatus for practising the present invention.

The invention is hereindescribed as embodied in a process of fractionating Coalinga crude which contains only about 25% of light material comprising a small quantity of gasoline, and a somewhat larger quantity of a commercial gas oil fraction, the remainder comprising about 30% lubricating stock and 45% asphalt.

With the crude is mixed a quantity of diluent, preferably a kerosene having a narrow range of boiling points of about 450 and 550 F. Kerosene is the preferred diluent for this particular crude because it can be easily separated from the gasoline and recovered for re-use in the process. Preferably, a suicient quantity of diluent is used to make the lighter components of the entire mixture approin'mately equal to the amount of asphalt, and'` accordingly, about 20 parts of kerosene are added to each parts of the crude. The crude is fed through a line 2 which connects with a kerosene supply line 4, both lines leading to a heater 6 in which the oil is heated to about 600 F; prior to being discharged into a column 8 The column 8 comprises a bottom stripping section Il)v having decks of the conventional boiling cap type and three rectifying sections, indicated at l2, I4 and I6. At the bottom of each of the rectiiying sections I4 and i6 is a stripping section represented at I8 and 20 respectively, each stripping section comprising a vapor pipe to permit vapors to pass from one rectifying section to the next, internal reflux decks 22, and a steam inlet pipe 24. Steam is introduced into the bottom of the column as indicated at 26. An overhead condenser 28 is used to condense the gasoline and a part of the condensate is removed as a product through the pipe 30 and the remainder is returned as reux through the pipe 32. 'Ihe kerosene is stripped of any light gasoline coinponents in the section 20 and is withdrawn by a pipe 34. Gas oil is withdrawn from an` intermediate deck of the section i4 by a pipe 36 and a stripped light lubricating stock is withdrawn from the stripping section I8 through a draw-off 33.

The residue, comprising the heavier lubricating stocks and asphalt, is withdrawn from the bot-v tom of the column through the pipe40 which joins the kerosene pipe 34. terials is heated in a pipe still 42 and is introduced into a final column 44. The process of separation of the lubricating components from the asphalt is carried out as described in my Patent No. 1,905,156. The column 44 has a bottom stripping section 46, into which steam is introduced at 48, and two rectifying sections 50 and 52. The rectifying sections preferably cornprise a series of staggered decks over which the reflux liquid may cascade in contact with the ascending vapors which take a tortuous course between the decks. At the bottom of the rectifying sections are side stripping sections 54 and 50 respectively. The column is operated under a moderate vacuum corresponding to an absolute p-ressure between '75 and 100 mm. of mercury. Under the heat contained in the mixture and With the steam introduced at 48, the oils including the lubricating stocks and diluent flash as a unit from the asphalt and the vapors ascend through the column. The kerosene is condensed in the vacuum condensing system 58 and a part thereof is returned through the pipe 60 to the column.

i* A lubricating stock of intermediate viscosity is withdrawn from the bottom of the stripping section 56 through the pipe 62 and lubricating stock of heaviest viscosity is withdrawn from the bottom of the section 54 by the pipe 64.

The amount of diluent not returned to the column through the pipe 60 is withdrawn by a pipe 66 which connects with the pipe 4 leading to the original crude feed.

It will be observed that the diluent is continuously recirculated through the process, being first used to facilitate the vaporization of the lighter and intermediate oils in the first column 8 and later used to enhance the flash vaporization of the oils in the iinal column 44.

It will be noted that with the proportions heretofore mentioned, a truly balanced mixture lcannot be obtained by the addition of kerosene alone. The addition of 20 parts kerosene to 100 p-arts crude gives 45 parts light material, 30 parts lubricating stock and 45 parts asphalt. A closer balance could be obtained by the addition of more lubricating stock but this is not necessary in practice.

In the example chosen, the use of kerosene as a diluent is particularly satisfactory. The kerosene may be easily separated by rectification from the lower boiling gasoline and the higher boiling gas oil, and may thus easily be recovered for continuous use in the process. Furthermore, since the crude contains little or no kerosene, the added kerosene fills the gap between gasoline and gas oil and forms a substantially continuous chain of components which facilitates flash vaporization of the lighter materials as a unit in 'the first column.

As a modification of the invention, a heavy The mixture of macrude of the Coalinga type may be mixed with an unbalanced light crude for reduction of. both to approximately balanced specifications. For example, a Kettleman Hills crude containing about 60% gasoline and 40% heavier materials, can be mixed in equal proportions with Coalinga. A1-

though this mixture may not be perfectly balanced vbecause of the preponderance of light components, it is satisfactory for good distillation. The balance may in fact be improved by subjecting the Kettlernan Hills crude to a preliminary distillation to remove some of the lighter gasoline components, and thereby to leave a crude having 40 to 50% gasoline, which is especially suitable for mixture with the heavy crude. In any event, the mixture of crudes is heated in the pipe still 6 and the operation in the first column is carried out as above described, gasoline being obtained as an overhead product, and kerosene, gas oil and a light lubricating stock, as side products. A part of the kerosene is then mixed with the residuum from the first column and is passed through the heater 42 and introduced into the nal column 44 in which the separation between the lubricating stock and the asphalt occurs.

Having thus described the invention, what is claimed is:

1. The method of fraotionating an unbalanced heavy crude oil having only a small proportion of light components and a large proportion of asphalt which consists in adding tothe crude a Y diluent of material as light as gas oil, heating the mixture, vaporizing the light material as a unit and leaving a residuum of lubricating stock and asphalt, fractionating the vapors to recover the diluent, mixing the diluent with the residuum, heating the mixture, vaporizing the lubricating stock and the diluent as a unit, separately condensing the lubricating stock and the diluent, and recycling the diluent to be added to the crude.

2. The method of fractionating an unbalanced heavy crude having only a small quantity of gasoline in comparison with the quantity of asphalt which consists in mixing the crude with an unbalanced light crude having a preponderance of gasoline with a relatively small quantity of heavy components, heating the mixture, vaporizing components of the gas oil and lighter ranges to leave a residuum of lubricating stock and asphalt, fractionating the vapors to obtain a diluent product of narrow boiling range and at least as light as gas oil, mixing the diluent with said residuum, heating the mixture, vaporizing the lubricating stock and the diluent as a unit, and separately condensing the lubricating stock and the diluent.

3. rIhemethod of fractionating an unbalanced heavy crude having only about gasoline and about 45% asphalt which consists in mixing therewith an unbalanced light crude having at least 40% gasoline, heating the mixture, Vaporizing oils of the gasoline, kerosene and gas oil groups to leave a residuum of lubricating stock and asphalt, fractionating the vapors to obtain a diluent product of narrow boiling range and at least as light as gas oil, mixing the diluent with said residuum, heating the mixture, vaporizing the lubricating stock and the diluent as a unit, and separately condensing the lubricating stock and the' diluent.

GEORGE B. COUBROUGH. 

